Gliederung

Objective

The purpose of this study was to evaluate the feasibility, benefit and limitations of intraoperative high-field magnetic resonance imaging (MRI) in epilepsy surgery.

Methods

In 40 patients undergoing surgery on temporal or extratemporal focal epilepsy MR imaging was performed using a 1.5T scanner. In 33 patients the suspected epileptogenic area was measured with intraoperative electrocorticography (ECoG) using surface strip electrodes and hippocampus electrodes in the temporal horn of the ventricle. Following MRI and ECoG measurements a tailored resection was performed. The extent of resection was demonstrated by intraoperative MR imaging and correlated with the early postoperative outcome.

Results

The MRI scanner did not interfere with the ECoG recorded close to the 5 Gauss zone. In pre- and postresection MR imaging neocortical and limbic anatomical structures could be shown with high resolution. Pathological MRI findings as hippocampus sclerosis, cortical dysplasia or low-grade tumors were shown in superior quality using the T2- transversal and coronal sequences. MR measurements with platinum strip electrodes in situ precisely exhibited the three-dimensional position of each electrode contact and gave the opportunity to delineate the center and the volume of the epileptogenic zone as recorded by the ECoG. Both the T2-transversal and the T1-MPRAGE sequence were best suitable for the imaging of ECoG-electrodes. No adverse side effects were seen after the combination of MRI and ECoG examinations.

Conclusions

The combined use of intraoperative MR imaging and electrophysiological measurements gives the opportunity to optimize the tailoring of epilepsy surgery in each individual. Patients harboring lesional pathologies or suffering from critical neuropsychological prerequisites are good candidates to profit from this technique, however, its true benefit cannot be proven statistically yet as long-term follow-up examinations with respect to seizure and neuropsychological outcome are still missing.